ZoBell — 36 — Marine Microbiology 



After plugging the ends of the sampler tubes with cotton, a number of 

 them can be sterilized in the laboratory ready for field use. Since the tube 

 is made of brass, the mud samples should be removed shortly after col- 

 lection, and the sub-samples should be taken from near the center of the 

 core. 



Storage of samples : — The storage of samples of water or mud is 

 usually accompanied by a slight decrease followed by a rapid increase in 

 the microbial population and a continuous decrease in the detectable num- 

 ber of species. These changes become apparent within an hour or two 

 after the collection of the samples and may continue for several days. 

 The magnitude of the changes is a function of the original composition of 

 the sample, the temperature, size of sample, availability of oxygen, ex- 

 posure to light, and other factors. 



Whipple (1901) found that the bacterial population of water, which 

 initially contained 77 bacteria per ml., decreased for a few hours and then 

 increased to as many as 41,400 per ml. after 24 hours' storage. He at- 

 tributed the initial decrease in the bacterial population to a dying off of the 

 less resistant species, since there was an actual decrease in the number of 

 species with time of storage. Agitation or continual shaking of the stored 

 samples was found to retard the multiplication of bacteria only slightly if 

 at all. 



Whipple (1901) noted that about 10 per cent of the bacteria in the 

 water were tenaciously attached to the walls of the glass receptacle after 

 24 hours' storage. After observing a far greater increase in the bacterial 

 population in water stored in small bottles than in large bottles, Whipple 

 attributed the increase to the more ready availability of oxygen, because 

 relatively more water was exposed to the air when stored in small recep- 

 tacles than in large receptacles. However, ZoBell and Stabler (1940&) 

 found that the multiplication of bacteria in stored lake water was inde- 

 pendent of the oxygen tension over a wide range, 0.30 to 36 mgm./L. 

 More recently ZoBell (19436) has summarized the evidence which indi- 

 cates that the more rapid multiplication of bacteria in small samples of 

 water is associated with the area of solid surface, small receptacles present- 

 ing considerably more solid surface per unit volume of water than 

 larger receptacles (see page 83). Similar conclusions were reached by 

 Lloyd (1937). 



The concentration and composition of organic matter in sea water are 

 also important factors which influence the changes in the bacterial popu- 

 lation during storage (Waksman and Carey, 1935a, ZoBell and Grant, 



1943)- 



Fred et al. (1924) attributed an observed increase in the bacterial pop- 

 ulation of stored lake water from 126 per ml. to 7,400,000 per ml. partly to 

 the death and decomposition of bacteria-feeding protozoans which were 

 unable to tolerate confinement. Heukelekian (1933) doubts whether 

 there are enough protozoans in diluted sewage to play an important role on 

 the number of bacteria during the storage of samples. 



After considering the influence of agitation, size of receptacle, temper- 

 ature, and other factors which influence the bacterial population of stored 

 samples, Butterfield (1933a) concluded that "the more interference 

 with normal conditions, the greater the increase in bacterial numbers." 

 He observed more rapid changes in samples stored at 37° and 20° C. than 

 in those stored at 10° C. 



